Development of Teeth Flashcards
teeth consist of 3 hard tissues
enamel, dentin, cementum
ectoderm gives rise to
ameloblasts that form enamel
neural crest cells give rise to
odontoblasts and cementoblasts which form dentin and cementum
mesoderm gives rise to
endothelial cells which form the inner lining of blood vessels
what occurs during the 6th week of gestation
formation of dental lamina in the upper and lower jaws
dental lamina is
a U-shaped thickening of the oral epithelium that follow the curves of the primitive jaws
development of teeth follow 3 stages
bud, cap and bell
bud stage
by 7th week
-dental lamina gives rise to 10 tooth buds in each jaw that grown into the underlying mesenchyme
-buds develop into deciduous teeth
what does each tooth bud consist of
a proliferation of ectoderm and the condensation mesenchyme surrounding it from neural crest cells
bud stage permanent teeth tooth buds
the tooth buds for permanent teeth that have deciduous predecessors begin to appear at approximately 10 weeks from deep continuations of the dental lamina that develop lingual to the deciduous tooth buds
since ______ _____ have no deciduous predecessors, they develop as ______ _______ of the dental laminae
permanent molars
posterior extensions
cap stage
the proliferated ectoderm of the tooth bud induces the formation of a mesenchymal hillock beneath it, called the dental papilla
bell stage
the proliferated ectoderm encloses the dental papilla to form a cap like structure called the enamel organ
mesenchyme surrounding the dental papilla and the dental lamina cap condenses to form the dental sac (dental follicle)
the enamel organ consists of
an outer cell layer called the outer enamel epithelium
the inner cell layer lining the papilla called the inner enamel epithelium
central core of loosely arranged cells in-between called the enamel reticulum or stellate reticulum
odontoblasts
the outermost cells of the dental papilla adjoining inner enamel epithelium differentiate into odontoblasts
cells go on to secrete predentine which then calcifies to become dentin
dentin secretion is triggered by
the inner enamel epithelium and begins at the apex of the tooth moving towards the neck
what happens to odontoblasts as dentine thickens
they regress to the center of the dental papilla leaving a thin cytoplasmic process (dental process) embedded in the dentin
what is the secondary dentine
when the odontoblast layer persists after tooth eruption and forms dentin throughout life
what is tertiary dentine
produced in response to stimuli like tooth damage, or by pulp cells or by odontoblasts
what forms the pulp of the tooth
the rest of the cells of the dental papilla
ameloblasts
differentiated cells of inner enamel epithelium
under the influence of odontoblasts these cells produce long enamel prisms over the dentin
what do the long enamel prisms over the dentin do
matures by increasing mineral content, after which the ameloblasts degenerate
root of the tooth development
develops after dentine and enamel
at the neck of the tooth the inner and outer enamel epithelia come together to form the epithelial root sheath
the sheath grows into the mesenchyme and initiates root formation
odontoblasts continue to lay down dentine and as the dentine increases, the pulp cavity narrows to form the root canal
dental sac derivatives
inner cells differentiate into cementoblasts which produce cement that is deposited over the dentine of the root and meets the enamel at the neck of the tooth
outer cells become active in bone formation as the jaws ossify
the alveolus (tooth socket) held by the periodontal ligament
cementum
the bone-like, mineralized connective tissue covering the root of the tooth
periodontal ligament
derived from neural crest cells
a specialized vascular connective tissue that surrounds the root of the tooth, attaching it to the alveolar bone
eruption
as the root of the tooth grows, its crown gradually erupts through the oral epithelium
which arch erupts first
mandibular teeth before maxillary
by the end of the _____ year all children usually have ___ deciduous teeth
second
20
what can cause delayed eruption
hypopituitarism
hypothyroidism
what gets resorbed by osteoclasts
the root of the corresponding deciduous tooth
what affects the shape of the face
the development of the paranasal sinuses and the growth of maxilla and mandible to accommodate teeth
natal teeth and why
erupted teeth at birth
usually lower incisors
neonatal teeth - 1 or more teeth erupt later in the neonatal period (1-4 weeks of life)
complications like maternal discomfort while breast feeding, laceration of the neonate’s tongue, aspiration of detached tooth
may need to be extracted and spacers required
enamel anomalies
enamel hypoplasia: nutritional deficiency, deficiency of Vit A and D during critical period (6-12 weeks), tetracycline therapy, infections like measles
amelogenesis imperfecta: aberrations in enamel formation, inherited ectodermal birth defect, mutational defects of genes - AMELX, ENAM, and MMP20
dentinogenesis imperfecta
can be caused by collagen type I mutations
can be associated with osteogenesis imperfecta
can lead to enamel fractures as the dentine is not hard enough to support the enamel
agenesis of maxillary permanent teeth
hypodontia: too few teeth
oligodontia: more than 6 teeth absent
anodontia: complete lack of primary and/or secondary teeth
supernumerary teeth: hyperdontia
mesioden: commonest supernumerary tooth between maxillary central incisors
may affect development of adjacent teeth
lateral incisor has contribution from medial nasal process and maxillary process. failure of fusion could cause two lateral incisors along with cleft lip
taurodont
increased formation of tooth body and pulp cavity with decrease in the length of the root
teeth with extra roots present challenges for
root canal therapy and extraction
